Revert "Use Codex styles for buttons in language overlay"

This reverts commit d29050d080.

Reason for revert: I had mistakenly assumed the @wikimedia/codex
module was loaded on clicking the language button. It appears to
be added on page load.

Given T248718 it's still unclear what our policy on loading
@wikimedia/codex on page load is and given several people are out
I think it would be better to attempt this again next week, possibly
delaying further if needed.

Bug: T353071
Bug: T248718
Change-Id: I09334a1faec06a7400e61013ddda374156bf5d72

resources/css/ext.uls.displaysettings.less

@@ -9,8 +9,7 @@
 .uls-button-group {
 	display: inline-block;
 	position: relative;
-	// The 1px are needed to handle overflow in .cdx-button-group in 1.39
-	padding: 1px 0 0 1px;
+	padding: 0;
 	left: -20px;
 	z-index: 1;
 }